Tasks for encoding sound information. Coding information Axistence of sound within 10 seconds

Information coding

One of the main lines in the teaching of informatics is the coding of information. This topic Complies with the basic objectives of the discipline "Informatics and ICT": the formation of ideas about information, ideas about the measurement of the amount of information in different types perception.

Depending on the method of perception of the task of encoding information is divided into three types: encoding images, text and sound. Any of the listed types of tasks is always present in GIA, EGE and Olympiads. Therefore, it is most important to figure out in this field of computer science.

Graphics

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Example . Calculate the volume of the video memory required for storage. raster imageHaving occupy the entire monitor screen with a resolution of 640x480 pixels if the palette is used from 65536 colors.

Decision. The color depth can be found according to the formula N \u003d 65536 \u003d 2i, it means that I \u003d 16 bits, therefore, to store one pixel, the image will be required 16/8 \u003d 2 bytes of video memory. Thus, for the storage of the entire image, you will need a VG \u003d W * H * i \u003d 640 * 480 * 2 \u003d 614400 byte \u003d 600 Kb.

Sound

Alphabet "HREF \u003d" / "REL \u003d" Bookmark "\u003e alphabet) as various possible equivalent states (events). Then everyone text symbol Any alphabet (letter, digit, punctuation sign, etc.) can be attributed to the code - an integer. Therefore, their information container depends on their number in the alphabet ( poweralphabet), the more their number, the greater the amount of information bears one character. For example, in the Russian alphabet (without the letter "E"), one character accounts for 5 bits of information (32 \u003d 2i) ..

Example. Determine the information volume of the proverb in the bits "small spool, yes roads", if the power of the alphabet is equal to 16 bits (without quotes).

Decision: You just need to calculate the number of characters in the proposal, without considering quotes, but including spaces. (At the same time, implying that there is one space between words, but there are no spaces for the punctuation of spaces). The resulting value is multiplied by i \u003d 4 bits. T. E. VT \u003d 22 * \u200b\u200b4 \u003d 44 bits.

These sections are an addition and generalization of each other, so when they are teaching, compliance should be compliance in theoretical presentation and when solving problems.

Task 2. . Determine the size (in bytes) of the digital audio file, the sound time of which is 10 seconds at a sampling frequency of 22.05 kHz and a resolution of 8 bits.

Task 3. Volume free memory On the disk - 5.25 MB, the discharge of the sound card - 16. What is the duration of the digital audio file, recorded with a discretization frequency of 22.05 kHz?

Task 4. Determine information volume stereo audio file duration of 1 second when high quality Sound (16 bits, 48 \u200b\u200bkHz).

Task 5. Determine the amount of memory for storing a digital audio file, the sound time of which is two minutes at a sampling frequency of 44.1 kHz and a resolution of 16 bits.

Task 6. One minute of recording of a digital audio file occupies 1.3 MB on a disk, the discharge of the sound card - 8. What frequency of sampling is the sound recorded?

Task 7. What amount of memory is required to store a digital audio file with high quality sound recording provided that the sound time is 3 minutes?

Task 8. The digital audio file contains a low-quality sound recording (the sound is grim and muted). What is the duration of the file of the file, if its volume is 650 kb?

Task 9. Two minutes of recording of a digital audio file occupy 5.05 MB on a disk. Discretization frequency - 22,050 Hz. What is the discharge of an audio adapter?

Task 10. The volume of free memory on the disk is 0.1 GB, the discharge of a sound card - 16. What is the duration of the digital audio file recorded with a sampling frequency of 44 100 Hz?

• Task 11. Evaluate the information volume of stereoadio file with a sound duration of 1 s (1 min) with high quality sound (16 bits; 48 kHz)
• Task 12. Calculate the monoadylfile sound time, if with a 16-bit coding and sampling frequency of 32kcs its volume is:
• A) 700 KB;
• B) 6300 KB.

1. The sound is a sound wave with a continuously changing amplitude and frequency. For a person, the sound is the louder than the longer the amplitude of the signal, and the higher the tone, the greater the frequency of the signal. The continuous signal does not carry the information in itself, so it should be turned into a sequence of binary zeros and units - binary (digital) code.

2. A sound digitization performs a special device on the sound card. It is called an analog-digital converter (ADC). Reverse Process - Playing the encoded sound is performed using a digital analog converter (DAC). Read more consider these processes.

In the process of coding continuous sound signal Discretization of time is made, or, as they say, "temporary sampling". The sound wave is divided into separate small temporary sections and a certain amount of amplitude is set for each site. This method called pulse-amplitude modulation of PCM (Pulse Code Modulation ). Thus, the smooth curve is replaced by the sequence of "steps". Each "step" is assigned a sound volume value (1, 2, 3, etc.). The larger the "steps", the greater the amount of volume levels will be highlighted during the encoding process, and the more information will be the value of each level and will sound better.

2. Characteristics of digitized sound.

The sound quality depends on the two characteristics - the depths of the sound coding and the sampling frequency. Consider these characteristics.

Sound coding depth ( I. ) - This is the number of bits used to encode various signal levels or states. Then the total number of such states or levels ( N. ) It can be calculated by the formula:

N \u003d 2. I.

Modern sound cards Provide a 16-bit sound coding depth, and then the total number of different levels will be:

N \u003d 216 \u003d 65536.

The sampling frequency (M) is the number of measurements of the sound signal level per unit of time. This characteristic shows the sound quality and accuracy of the binary coding procedure. Measured in Hertz (Hz). One measurement in one second corresponds to the frequency of 1 Hz, 1000 measurements in one second - 1 kilohertz (kHz). The sampling frequency of the beep can take values \u200b\u200bfrom 8 to 48 kHz. At a frequency of 8 kHz, the quality of the discretized sound signal corresponds to the quality of radio broadcasts, and at a frequency of 48 kHz - the quality of the audio soundCD.

High sound quality is achieved with a sampling frequency of 44.1 kHz and a sound coding depth of 16 bits. For gloomy, muted sound, the following parameters are characteristic: the sampling frequency is 11 kHz, the depth of coding is 8 bits.

In order to find the amount of sound information, you must take advantage of the following formula: V \u003d.M *I *t. where M is the sampling frequency (in Hz), I. - coding depth (in bits), t. - Sound time (in seconds).

Example

The sound is reproduced for 10 seconds at a discretization frequency of 22.05 kHz and a sound depth of 8 bits. Determine its size (in bytes). Decision:

M \u003d 22.05 * 1000 \u003d 220500 Hz;I \u003d 8/8 \u003d 1 byte;

T \u003d 10 seconds; V. \u003d 220500 * 10 * 1 \u003d 220500 bytes.

№1

Determine the amount of memory for the storage of monoadiophile, the sound time of which is five minutes at a sampling frequency of 44 kHz I.Glubine coding 16 bits.

Decision:

V \u003d Mit. \u003d 44000Hz * 16 * 5 \u003d 3520000 bits \u003d 430 KB.

Answer: 430 KB.

№2

What should be the sampling frequency and the coding depth for "recording sound information with a duration of 2 minutes, if the user has a memory of 5.1 MB.

Decision:

M * i \u003d V / T;

M * i \u003d 5.1 * 1024 * 1024 * 8/2 / 60 \u003d 356515 (Hz * bits).

Option 1

356515 (Hz * Bit) \u003d 22.05 kHz * 16 bits.

Answer: 22.05 kHz and 16 bits.

Option 2.

356515 (Hz * Bit) \u003d 44.1 kHz * 8 bits.

Answer: 44.1 kHz and 8 bits.

№3

The amount of free memory on the disk is 5.25 MB, coding depth - 8. Sound information is recorded with a sampling frequency of 44.1 kHz. What is the duration of the sound of such information?